Glass-aged cocktails

It was in 2004 after receiving a 1920s bottle of Dubonnet that I first decided to age a series of classic cocktails in small barrels with different proportions. I had been amazed how good the 1920s Dubonnet tasted - the residual air in the bottle had both matured and mellowed the flavours.

I was struck by the thought that the evolution of drinks is almost Darwinian: the best ones outlast their competition and many have survived from before the turn of the century. With the theory of evolution in mind, I then wondered if it were possible to make the best ones even better, without changing the obvious components of product and proportion.

I mixed Rusty Nails, Martinis and Manhattans in different proportions and rested them in wooden barrels. I wanted to see how far I could go with it, but after frequent taste tests of the results, I was disappointed. Since I considered it a failed project I laid it to rest, without putting it into the public forum. The way I saw it, you win some you lose some, and as food technologist Harold McGee later pointed out to me: "Why add wood to wood?" I couldn't agree more.

With most ideas, there is an overlap with past creativity, and this may be discovered retrospectively or it can be used as inspiration for a new creative direction, and in turn encourage a new wave of ideas. This was exactly the case when the ever-cheeky David Wondrich handed me a folded copy of a Club Cocktail advertisement, circa 1912, just moments before I went on stage to talk about vintage cocktails at the Berlin Bar Show in 2010. It read as follows:

"CLUB COCKTAILS for your friends this Christmas.Soft as the shadows of firelight, fragrant as the birch log on the hearthGolden drink in keeping with the joy of Christmas time.CLUB COCKTAILS are mixed to measure - by experts - of selected liquors. Then they are aged in wood."

It turned out that Club Cocktails were aged for three months, then sold in the bottle. Before I had read this I had no idea that barrel-aging cocktails had already been experimented with by some turn-of-the-century bright spark.

The inspiration for barrel-aging might be Victorian, but we now possess the knowledge and technology to both know better and make quality products that are consistently good and this is something which should be incredibly important to a bar. Bartenders are taking the time to research barrel-aging - Darcy O'Neil's findings in particular have become an invaluable source. However, barrel-aging is not a debate that I consider to be about classicism, but rather it is simply about what tastes good, and how ingredients can be changed to expand their flavour profile.

BOTTLING IT UP

Having personally abandoned the barrel-aging experiment, I was still very much interested in producing a cocktail that could achieve a balance between smoothness and an enormous body. At the same time as laying down cocktails in the barrels I also put the same cocktails into a large number of bottles. I knew that Jerry Thomas used to bottle his cocktails and sell them as 'take-away'. However, the bottled cocktails were not made to age. They weren't stored on the mantle-shelf and left to mature; they were for consuming outside of the bar, as soon as possible and with much relish I would imagine.

After reading a number of papers, I had been particularly inspired by a piece written by Harold McGee which talked about the effect of oxidisation on wine. In this way, the continuation of the discarded barrel-aging project took its cue from the concept of aging wine or port by careful control of oxidation - a positive oxidisation. Rather than the Club Cocktails range, which were aged for three months in a barrel and finished off in the bottle, this aged cocktail would spend its entire gestation safely inside a glass bottle, achieving an annual vintage as you would a port. With this in the back of my mind, it was a further six years of experimentation with glass bottles that led to that cheeky exchange behind the scenes of the Berlin Bar Show.

Using the Manhattan as my starting point, my aim was to refortify the sweet vermouth using the bourbon. So I mixed together ten different bottles of sweet vermouth, bourbon and bitters, allowed a certain amount of air to enter, then sealed them and lay them down in a dark cellar. After three months I found the result was dire and gave up on the project as another failed experiment. However, much later when clearing out the cellar, I came across my forgotten bottles. I was about to throw them away when I thought to taste them. To my surprise, the flavours had blended together perfectly to give a mellower and smoother cocktail. I made a new batch in preparation for the next few years, and have since laid down Harvards and El Presidentes, both of which have been an enormous success in the bar.

POSITIVE OXIDISATION AND BEYOND

I then went to a flavour company to confirm the results of what we thought was happening to the alcohol once left inside the bottle, and were told we were the first people to ever get cocktails gas chromatographed. The results confirmed what we had been thinking: when left inside the bottle, the chemicals of the alcohol react and break down one another. They do this in peaks and troughs, and become smaller as they integrate. The more aggressive the flavour, the higher the peaks, and this makes for big flavour. Over time, the chemicals continue to react but with smaller peaks and troughs that go on for longer. These smaller reactions entail that the drink is incredibly smooth. The increased number of chemical reactions makes the chromatograph reading a lot longer.

Aging in glass doesn't pretend to obtain the same results as aging in the barrel. We are not trying to impart any new flavours to the cocktail, but rather to encourage a new direction for the flavours that are already present. There are no quick fixes to achieve this, resting the cocktail for weeks just doesn't cut it, they have to sit for much much longer - but the results are truly worth the wait. I'm now in possession of an extraordinary range of vintages, from six months to almost eight years, and the next few months will see the release of the five-year and incredible eight-year vintages at 69 Colebrooke Row. From what I've tasted, you simply can't achieve the same complexity from a few weeks in wood or steel compared to what eight years in glass can do.

Since 2009, I've been looking into new methods of aging cocktails. We've stripped the wood out of the Manhattan using a rota vapour, and then re-aged it by adding staves to the bottle. At the lab we have also been experimenting with flash-fusing the ingredients of the Manhattan together. This is done according to the principle of how molecules respond to temperature. The more you heat an atom the less stable the atom becomes, the protons and electrons become more volatile and vibrate until they reach a point at which they cannot hold on to one another and break apart. As the vibrations increase, the molecules bounce into one another and create new bonds. This makes them blend much more quickly.

ON BECOMING A GLOBAL TREND

The global interest in aging cocktails has started a new conversation - the latest stage in a discussion that began a hundred years ago. This kind of open forum allows us as bartenders to look at what we do from a different perspective. I think that's always a positive thing - creativity is born from communicating ideas - both new and old, and then twisting them round, turning them on their head. It's become something of a mantra for me.

If you wanted to consider which cocktails you might try aging, my suggestion would be to take a real hard look at the flavour profile of the drink. This takes time. Then ask yourself whether this is an idea that sounds impressive on a cocktail menu or if it's a drink that is really going to work? Is it a marketable concept, or is it a tasty beverage?

What concerns me about the aging trend is that it has become more about the package than the content. It appears now that there are a multitude of bartenders serving up aged cocktails, with little understanding of how and why they work. Displaying the barrels on the bar itself for example, leaves them open to constant temperature fluctuation, changing the flavour daily with no control over the results. If you endeavour to take on a project without understanding the process behind it, you can't pass on that knowledge to the customer. The bartending profession pivots on this action - the bartender is an informant, imparting the story behind the drink and the reason for why it just tastes so good. This accounts for a large proportion of what makes the experience and the product more enjoyable for the customer.

For me, the debate between barrel-aging, steel-aging and bottle-aging is a moot point - an aged cocktail is not a superior product, it is just different. Hopefully the dialogue will spawn a new generation of bartenders interested in the science behind alcohol, with the patience to study and wait for the results. But like I say, it takes time.